Wiring an RTU

[tyha]

we have an RTU that was not marked and the mech cont is not availible. Comming inside the unit we were told , of course, because this is a an RTU the heat strips are part of the unit and are put together with this box that looks like where we come in at. this box isnt attached to anything but has 3 lugs with 60 amp fuses comming off each and wires going outthe other side. Im assuming the mechanical cont wires past the fuses but my question is because nothing is mrked on the outside of the unit and the plans call for #4's with an 80/3 CB can we feed with 60 amp because that is what it is fused at anyway. the plans on this project have been wrong in almost all other areaes due to a load of changes. Im guessing the box is called a connector box or something that connects the comp and the heat strips

 

[chris kennedy]

this box isnt attached to anything

Just floating in space???

Often when heat strips are added you wire to the lugs on the fuse block then the wires leaving are a harness, part of which go to the contactor you would normally wire to.

The unit name plate will have multiple MCA and MOP listed and should have been marked when the heater was installed. Match up the model number of the heat strip with the RTU name plate.

 

[tyha]

Just floating in space???

Often when heat strips are added you wire to the lugs on the fuse block then the wires leaving are a harness, part of which go to the contactor you would normally wire to.

The unit name plate will have multiple MCA and MOP listed and should have been marked when the heater was installed. Match up the model number of the heat strip with the RTU name plate.

we wired from the ds to this fuse block. I know about MCA and MCB thats how i size my wire and breaker but it wasnt marked

 

[ksmith846]

First considering nothing has been labeled, I would make the GC or owner have the MC provide the proper info for unit.

Otherwise I would pull the heat strip and figure out it's KW rating. Then I would see if I could read an amperage from the label on the blower motor. I would then do my math to determine the proper wire and OCP size and wire accordingly.

Finally, if that info was not clear I would connect it per the plans and continue to try and get in touch with the MC to provide the proper information.